Re: Compiler Design in C How about it?

mike@thor.acc.stolaf.edu (Mike Haertel)
Tue, 5 Jun 90 17:40:09 GMT

          From comp.compilers

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Re: Compiler Design in C How about it? markh@squirrel.labs.tek.com (Mark Henderson) (1990-06-04)
Re: Compiler Design in C How about it? tbrakitz@phoenix.princeton.edu (1990-06-04)
Re: Compiler Design in C How about it? mike@thor.acc.stolaf.edu (1990-06-05)
Re: Compiler Design in C How about it? napi@rangkom.MY (1990-08-07)
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Newsgroups: comp.compilers
From: mike@thor.acc.stolaf.edu (Mike Haertel)
References: <1990Jun1.194941.5781@esegue.segue.boston.ma.us> <1990Jun4.044858.15066@esegue.segue.boston.ma.us> <1990Jun4.212544.18596@esegue.segue.boston.ma.us>
Date: Tue, 5 Jun 90 17:40:09 GMT
Organization: Free Software Foundation
Keywords: books, optimize

In article <1990Jun4.212544.18596@esegue.segue.boston.ma.us> tbrakitz@phoenix.princeton.edu (Byron Rakitzis) writes:
>I've heard quite the opposite from Richard Stallman about his GCC
>compiler, paradoxically enough: he claims that there are more bugs in
>"gcc" as opposed to "gcc -O" since most of the time gcc users turn the
>optimizer on (and hence have uncovered the optimizer bugs) and also
>that the optimizer tends to hide a few bugs in the code generator by
>never letting it generate the bad code in the first place!


There have indeed been substantially worse problems with the code generator in
GCC than there have with the optimizer. Or at least, this is the impression I
have gotten in conversations with RMS.


The optimizer has a rather more well-defined problem: Optimizing sequences of
RTL instructions. The code generator has to produce those instructions in the
first place, and it does so with a variety of ad-hoc techniques that are
severely conditionalized on the characteristics of the target machine. The
use of ad-hoc techinques as opposed to more uniform strategies is obviously a
potentially very rich source of bugs.


The optimizer, in contrast, deals with the same RTL language for all target
machines, and also uses more well-defined algorithms from the literature.


--
Mike Haertel <mike@acc.stolaf.edu>
--


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